The present invention relates to a circuit arrangement for the compensation of crosstalk in a digital communications system, particularly to line equipment including transmitting and receiving circuits. Compensation of crosstalk from a transmitting to a receiving circuit for one subscriber is disclosed in DE 3,343,584.A1, however the features of the present invention relating to the compensation of crosstalk from transmitting circuits to receiving circuits of different subscribers are novel.
In line-bound electrical communications some of the signals are transmitted over pairs of conductors that are combined in a line cable. In a four-wire transmission the outgoing and the incoming line are disposed in one and the same cable perhaps even in a star-quad arrangement within the cable. Depending on subscriber density, a large number of transmission lines are accommodated in such a cable and, due to the cable configuration, they are subject to crosstalk. Such interference has an adverse effect on the communications and, particularly if the transmission of digital signals between data processing devices is involved, may lead to errors in signal content.
A known way to suppress crosstalk in a cable is to utilize only some of the lines for the transmission and/or to adjust the occupation of the lines in a cable by trial and error until a minimum amount of crosstalk is obtained.
Such methods are very expensive and do not systematically result in crosstalk suppression.
DE 3,343,584.A1 discloses a crosstalk compensation circuit between an outgoing and incoming subscriber line. In this prior art circuit, part of the transmitted signal is branched off and a compensation signal is obtained by way of an adaptive filter and an inverter and is then added to the signal received by the subscriber.
This prior art circuit has the drawback that it is able to compensate only for the crosstalk existing between the outgoing and incoming lines of an associated transmitting and receiving device provided for two-way communication.